ECOLOGY OF HIGH-ALTITUDE ENVIRONMENTS: BIODIVERSITY, DYNAMICS, AND ANTHROPIC IMPACTS

A wide variety of organisms has been proven to thrive on the surface of glaciers and ice sheets, which have been proposed to be a proper biome. The glacial organisms described include a wide variety of taxa, which also show geographical variations in their distribution. Given the recency of this branch of research, a lot of questions still need to be answered, ranging from the taxonomical classification of many species detected on glaciers, to the biogeographical patterns of their distribution and the ecosystem services these organisms provide. This thesis is an attempt to contribute to the answer to some of these questions. We will first analyse biogeographical patterns in bacterial communities of cryoconite holes, finding that each glacier hosts a distinct bacterial community, even when glaciers are only a few hundred metres apart. This variation is higher than the seasonal and year-to-year variation of cryoconite holes bacterial communities that occurs on some glaciers and suggests a biogeographical pattern of distribution. Then, we will describe the trophic interactions that occur and shape the functioning of a model glacier ecosystem (the Forni Glacier), determining the importance of cyanobacteria and algae as primary producers, and of springtails and tardigrades as consumers. The following section is dedicated to contaminants, including sources of contamination (e.g., ski infrastructure) and their effects on microplastic contamination, latitudinal patterns in microplastic contamination at different sites, and metal and persistent organic contamination on the Alps. Our results show that ski infrastructure has a significant effect on microplastics concentrations, shape, and composition, and that latitude may be a factor in explaining the distribution of microplastics at a broader scale. In contrast, contamination by metals and persistent organic pollutants at Alpine scale seems to be mainly driven by local sources. The last section investigates the effects of pollutants of the glacier biota, by means of direct measurements of radioisotopes bioavailability and their uptake by glacier biota, and of a review of literature to assess the risk due to a broader number of contaminants.